1. Field of the Invention
The present invention relates to a wired transmission line for AV devices. More specifically, the present invention relates to a wired transmission line used for AV devices having a millimeter-wave communication function.
2. Description of the Related Art
In recent years, a wired transmission system which transmits and receives uncompressed video data and uncompressed audio data (hereinafter also referred to as audio visual (AV) data) between high-definition multimedia interface (HDMI)-connected devices has been put to practical use.
Further, based on digital living network alliance (DLNA: registered trademark) technical specifications, communication of AV data between devices using a home LAN (home network) in particular has also been performed. Further, there is also an increasing demand for downloading the AV data onto a portable device at high speed.
Millimeter-wave communication capable of performing Gbps-order transmission has received attention in order to transmit AV data at high speed under these circumstances.
Then, an audio and visual device (hereinafter also referred to as an AV device) which includes a millimeter-wave communication module and is premised on millimeter-wave wireless AV data transmission has been proposed.
However, it is difficult for the AV device capable of millimeter-wave wireless AV data transmission to ensure a stable communication path when a wireless communication path in a free space from a transmission portion to a reception portion cannot be ensured due to a surrounding environment or a condition in which the AV device is installed, or because of interference among a plurality of similar devices which use millimeter-wave wireless AV data transmission. In such a case, AV data transmission may not be performed.
When the wireless communication path cannot be ensured in the free space, there is provided a method of switching connection between an antenna and a transmitter/receiver to wired connection using a millimeter-wave waveguide such as a coaxial line to ensure the communication path. Alternatively, there is also provided a method of switching an output destination of a video signal inside the AV device from a radio transmitter/receiver to a wired transmission system using an HDMI cable, for use, for example.
Japanese Patent Application JP 2008-252566, for example, proposes a method of stacking a plurality of AV devices one atop another, installing the stacked AV devices, and changing a radiation direction of a millimeter wave to allow communication even if the millimeter-wave transmission/reception unit of an AV device is shielded by an electromagnetic wave shielding object. This method has been proposed to deal with shielding of an antenna opening surface.